1. Field of the Invention
The present invention relates to surge protection devices applied to or used in a power supply system, and specifically for spark gap surge protection devices. The surge protection devices are mainly applied in Class I and Class II surge protection of power supply systems such as power distributors, cell sites, and power transfer stations. The surge protection devices provide for the protection of surge currents and voltages traveling to electronic equipment and systems. The surge currents and voltages are caused by lightning, transient over-voltages and operation over-voltages, which can all cause the breakdown of electronic equipment and systems.
2. Description of Related Art
Several different types of surge protection devices have been used to protect electronic components from sudden surge currents or voltages caused by lightning or other sources.
A first type of surge protection device is a metal oxide varistor surge protection device (MOV SPD). The MOV SPD has been widely applied to or used in a variety of fields to protect against surge currents and voltages. When the MOV SPD is stricken by high surge energy, it is easily broken down by thermal runaway or an electronic current impulse strike. The withstanding capability of Class I current impulse SPDs under IEC 61643-1 (2005) (Low-voltage surge protective devices—Surge protective devices connected to low-voltage power distribution systems—Requirements and tests) is no more than 20 kA (10/350 us). To maintain good application results, the MOV SPD includes a coated or sealed MOV with a suitable power lead.
A second type of surge protection device is a spark gap surge protection device with an auxiliary discharging trigger (SG SPD). The SG SPD has been widely applied to or used in a variety of fields to protect against surge currents and voltages. For example, when the SG SPD is applied to a power supply system, the main concern is the problem of the follow current. That is, when the SG SPD is turned on by the surge current and over-voltage, the surge current is discharging to the ground through the SG SPD; however, the SG SPD does not address how to quench the arc or how to turn off the follow current in a safe way—this problem is addressed or solved by the present invention.
For a single SG SPD, when there is a discharging current in the gap, a transient high temperature arc is produced or exists in the gap and makes one of the insulating materials, named Gas-Evolving Insulating Materials, release a special gas. This special gas pressure increases rapidly to generate a sudden gas flow in the gap. This gas flow creates a gas flow arc voltage between the electrodes of the SG. When the gas flow arc voltage value is greater than a voltage value of the power supply, the arc is quenched. This describes how the single SG works as the SPD.
There are two different kinds of SG SPDs. The first one has a higher arc trigger voltage with a higher residential voltage of more than 3,000V and a lower protection level. The first one cannot protect the system and equipment against the surge well. The second one has a transient high temperature arc and a high pressure gas flow. The second one includes the Gas-Evolving Insulating Material and strength of mechanics cavity with a complicated manufacturing process.
A third type of surge protection device is a surge protection device having multiple serial gaps with capacitors as the divide voltage discharging chain. As there are multiple gaps in serial, the whole arc voltage is the single gap arc added as the serial chain so the whole arc voltage is higher than the single spark gap arc's voltage. When the whole arc voltage is higher than the source power voltage (peak value), the arc is quenched in time. Currently, two kinds of multiple spark gap SPDs exist in the China market. The first one is a high efficiency overlap graphite gap SPD (China Patent No. CN 101090197A). The second one is a lightning discharging spark gap SPD (China Patent No. CN 1377108A). These two kinds of SPDs have at least two significant drawbacks. The first drawback is that the discharge voltage is not stable and the residential voltage is higher than 2,500V (if it is tested by IEC 61643-1 (2005) 1.2/50 us@ 6 kV). The second drawback is that it is difficult to control the discharging energy, when it is tested by class I current wave 10/350 us strike, and the capacitor is easy to breakdown and in the worse case it is easy to explode.
Thus, there is a need to provide a surge protection device with improved qualities and functionalities.